It is critically important to control pressure in a processing chamber of semiconductor manufacturing equipment. Conventionally, in thin film formation apparatuses employing a chemical vapor deposition method, such as a plasma CVD apparatus or a low pressure CVD apparatus, APC (Automatic Pressure Control) is widely employed for controlling pressure in a processing chamber (see, for example, Patent Document 1).
Generally, in such an APC method, a conductance valve configured with, for example, a butterfly valve, is provided on an exhaust path connecting the processing chamber and a vacuum pump. The valve opening level of the conductance valve is variably controlled by a pressure feedback method. More specifically, the valve opening level of the conductance valve can be changed to an arbitrary value within a predetermined range of, for example, 0° (fully closed position)-90° (fully open position) with a motor controlled by a controller. A signal (instantaneous pressure level) output from a pressure detector such as a vacuum gauge attached to the processing chamber is fed back to the controller, and the controller variably controls the valve opening level of the conductance valve with the motor so that a measured pressure value matches a specified value.
In recent years, the ALD method has been attracting interest as an important film formation technology in manufacturing semiconductor apparatuses (see, for example, Patent Document 2). The ALD method is particularly advantageously applied in fields such as film formation of barrier metals used in wiring structures of semiconductor apparatuses and high dielectric films used as a gate insulating film of a MOSFET or a capacity insulating film of a capacitor. In the ALD method, a conductive film or an insulating film described above is formed by depositing a thin film by one atomic layer at a time on a processing object substrate such as a semiconductor wafer. Thus, unlike other vapor deposition methods in which a fixed amount of reactive gas is substantially continuously supplied into a processing chamber, in the ALD method, two types of reactive gas are alternately and intermittently supplied into the processing chamber at time intervals of a few seconds with purge gas supplied between the two types of reactive gas, and a layer or one atom or one molecule is formed in one cycle due to a chemical reaction of both reactive gasses. The thickness of a thin film formed on a substrate can be arbitrarily controlled by the number of times this cycle is repeated.
Patent document 1: Japanese Laid-Open Patent Application No. H7-142392
Patent document 2: Japanese Laid-Open Patent Application No. H6-080873